Biomedical Research Facility 2, School of Medicine, University of California, San Diego, Medical Sciences Research Bldg, 9500 Gilman Drive, La Jolla, CA 92093-0613C, USA; University of Gothenburg, Wallenberg Laboratory, Department of Molecular and Clinical Medicine, Institute of Medicine, Gothenburg, Sweden.
Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, Malet Street, London WC1E 7HX, UK.
Biochim Biophys Acta Mol Cell Res. 2020 Mar;1867(3):118440. doi: 10.1016/j.bbamcr.2019.02.003. Epub 2019 Feb 7.
The sarcomere is the basic unit of the myofibrils, which mediate skeletal and cardiac Muscle contraction. Two transverse structures, the Z-disc and the M-band, anchor the thin (actin and associated proteins) and thick (myosin and associated proteins) filaments to the elastic filament system composed of titin. A plethora of proteins are known to be integral or associated proteins of the Z-disc and its structural and signalling role in muscle is better understood, while the molecular constituents of the M-band and its function are less well defined. Evidence discussed here suggests that the M-band is important for managing force imbalances during active muscle contraction. Its molecular composition is fine-tuned, especially as far as the structural linkers encoded by members of the myomesin family are concerned and depends on the specific mechanical characteristics of each particular muscle fibre type. Muscle activity signals from the M-band to the nucleus and affects transcription of sarcomeric genes, especially via serum response factor (SRF). Due to its important role as shock absorber in contracting muscle, the M-band is also more and more recognised as a contributor to muscle disease.
肌节是肌原纤维的基本单位，介导骨骼肌和心肌的收缩。两个横向结构，Z 盘和 M 带，将细（肌动蛋白和相关蛋白）和粗（肌球蛋白和相关蛋白）丝固定在由titin 组成的弹性丝系统上。大量的蛋白质被认为是 Z 盘的整合或相关蛋白，其在肌肉中的结构和信号作用得到了更好的理解，而 M 带的分子成分及其功能则定义得较少。这里讨论的证据表明，M 带对于在活跃的肌肉收缩过程中管理力的不平衡很重要。它的分子组成是精细调整的，特别是就肌球蛋白家族成员编码的结构连接子而言，并且取决于每种特定肌纤维类型的特定机械特性。来自 M 带的肌肉活动信号传递到细胞核，并影响肌节基因的转录，特别是通过血清反应因子（SRF）。由于其在收缩肌肉中作为减震器的重要作用，M 带也越来越被认为是肌肉疾病的一个贡献因素。
